When would you consider CT aortic valve calcium score over TEE to further delineate the severity of LFLG aortic stenosis?
If the concern is for classical low flow low gradient severe AS (LVEF < 50%, AVA < 1 cm2 by echocardiogram with peak velocity < 4 m/s or mean gradient < 40 mmHg coupled with low stroke volume index, < 35 ml/m2), would recommend dobutamine stress echocardiography to distinguish between pseudo severe AS and true severe AS. If the patient is in rapid atrial fibrillation or there is clinical concern re: use of dobutamine (ACS or high-risk coronary disease), cardiac CT for AV calcium scoring is preferred. If there is concern for paradoxical low flow low gradient (LVEF > 50%, AVA < 1 cm2, peak velocity < 4 m/s, mean gradient < 40 mmHg and LVSI < 35 ml/m2), AV calcium scoring is the important modality of choice. While TEE can be helpful for direct 3D planimetry (2D planimetry should not be used as routinely overestimates AVA) when there are serial lesions (HOCM and severe AS) and echo hemodynamic parameters cannot be used, it will not help distinguish between pseudo-severe AS and true severe AS. In pseudosevere AS, the valve does not open well so the planimetered AVA will remain low. It will increase with alterations in loading conditions so feasibly a dobutamine TEE could be used however given that AV calcium scoring has been shown to independently correlate with AS severity and outcomes, AV calcium scoring should be the first test of choice.